1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly to a structure and driving method of a plasma display panel.
2. Discussion of the Related Art
Generally, a plasma display panel has higher definition than a cathode ray tube (CRT), various sized screens, and a thin thickness. In this respect, the plasma display panel has lately attracted considerable attention as the most practical next generation display of flat panel displays. Also, since the plasma display panel has a weight of ⅓ of a CRT having the same sized screen, a large sized panel of 40 inch to 60 inch can thinly be fabricated at a thickness of 10 cm or below.
The CRT and a liquid crystal display device are limited by their sizes when digital data and full motion are displayed at the same time. However, the plasma display panel does not have such a problem. Furthermore, the CRT may be affected by magnetic force. However, the plasma display panel is not susceptible to magnetic force, thereby providing stable images to viewers. Moreover, since each pixel of the plasma display panel is digitally controlled, image distortion of corners on a screen does not occur. Thus, the plasma display panel can provide higher picture quality than the CRT.
The plasma display panel includes two glass substrates coated with electrodes, and a gas sealed between the glass substrates. The electrodes formed in the glass substrates oppose each other in vertical direction, and pixels are formed in crossing portions of the electrodes.
A related art plasma display panel of three-electrode area discharge type will be described with reference to the accompanying drawings.
As shown in FIG. 1a, the related art plasma display panel of three-electrode area discharge type includes an upper substrate 10 and a lower substrate 20 which face each other. FIG. 1b shows a sectional structure of the plasma display panel shown in FIG. 2, in which the lower substrate 20 is rotated by 90°.
The upper substrate 10 includes scan electrodes 16 and 16′, sustain electrodes 17 and 17′, a dielectric layer 11, and a protection layer 12. The scan electrodes 16 and 16′ are formed in parallel to the sustain electrodes 17 and 17′. The dielectric layer 11 is deposited on the scan electrodes 16 and 16′ and the sustain electrodes 17 and 17′.
The lower substrate 20 includes an address electrode 22, a dielectric film 21 formed on an entire surface of the substrate including the address electrode 22, an isolation wall 23 formed on the dielectric film 21 between the address electrodes, and a phosphor 24 formed on surfaces of the isolation wall 23 in each discharge cell and of the dielectric film 21. Inert gases such as He and Xe are mixed in a space between the upper substrate 10 and the lower substrate 20 at a pressure of 400 to 600 Torr. The space forms a discharge area.
The scan electrodes 16 and 16′ and the sustain electrodes 17 and 17′ are of transparent electrodes and bus electrodes of metals so as to increase optical transitivity of each discharge cell, as shown in FIGS. 2a and 2b. That is to say, the electrodes 16 and 17 are of transparent electrodes while the electrodes 16′ and 17′ are of bus electrodes.
FIG. 2a is a plane view of the sustain electrodes 17 and 17′ and the scan electrodes 16 and 16′, and FIG. 2b is a sectional view of the sustain electrodes 17 and 17′ and the scan electrodes 16 and 16′.
A discharge voltage from an externally provided driving integrated circuit (IC) is applied to the bus electrodes 16′ and 17′. The discharge voltage applied to the bus electrodes 16′ and 17′ is applied to the transparent electrodes 16 and 17 to generate discharge between the adjacent transparent electrodes 16 and 17. The transparent electrodes 16 and 17 have an overall width of about 300 μm and are made of indium oxide or tin oxide. The bus electrodes 16′ and 17′ are formed of a three-layered thin film of Cr—Cu—Cr. At this time, the bus electrodes 16′ and 17′ have a line width of ⅓ of a line width of the transparent electrodes 16 and 17.
FIG. 3 is a wiring diagram of scan electrodes (Sm−1, Sm, Sm+1, Sn−1, Sn, Sn+1) and sustain electrodes (Cm−1, Cm, Cm+1, . . . , Cn−1, Cn, Cn+1) arranged on the upper substrate. In FIG. 3, the scan electrodes are insulated from one another while the sustain electrodes are connected in parallel. Particularly, a block indicated by a dotted line in FIG. 3 shows an active area where an image is displayed and the other blocks show inactive areas where an image is not displayed. The scan electrodes arranged in the inactive areas are generally called dummy electrodes 26. The number of the dummy electrodes 26 are not specially limited.
The operation of the aforementioned AC type plasma display panel of three-electrode area discharge type will be described with reference to FIGS. 4a to 4d. 
If a driving voltage is applied between the address electrodes and the scan electrodes, opposite discharge occurs between the address electrodes and the scan electrodes as shown in FIG. 4a. The inert gas injected into the discharge cell is instantaneously excited by the opposite discharge. If the inert gas is again transited to the ground state, ions are generated. The generated ions or some electrons of quasi-excited state come into collision with a surface of the protection layer as shown in FIG. 4b. The collision of the electrons secondarily discharges electrons from the surface of the protection layer. The secondarily discharged electrons come into collision with a plasma gas to diffuse the discharge. If the opposite discharge between the address electrodes and the scan electrodes ends, wall charges having opposite polarities occur on the surface of the protection layer on the respective address electrodes and the scan electrodes, as shown in FIG. 4c. 
If the discharge voltages having opposite polarities are continuously applied to the scan electrodes and the sustain electrodes and at the same time the driving voltage applied to the address electrodes is cut off, area discharge occurs in a discharge area on the surfaces of the dielectric layer and the protection layer due to potential difference between the scan electrodes and the sustain electrodes as shown in FIG. 4d. The electrons in the discharge cell come into collision with the inert gas in the discharge cell due to the opposite discharge and the area discharge. As a result, the inert gas in the discharge cell is excited and ultraviolet rays having a wavelength of 147 nm occur in the discharge cell. The ultraviolet rays come into collision with the phosphors surrounding the address electrodes and the isolation wall so that the phosphors are excited. The excited phosphors generate visible light rays, and the visible light rays display an image on a screen.
One pixel includes a discharge cell having a red phosphor, a discharge cell having a green phosphor, and a discharge cell having a blue phosphor. Contrast of an image displayed in the plasma display panel is controlled by the number of times of discharge in each discharge cell.
In the plasma display panel, priming effect is used to generate discharge in each discharge cell. In this case, priming particles, such as free electrons, ions, and quasi-stable atoms, are required. If electric field is sufficiently applied to the electrons, movement of the electrons is accelerated. When the electrons accelerated at a constant speed or greater come into collision with gas atoms or quasi-stable gas atoms, the gas atoms or the quasi-stable gas atoms can be ionized. Then, there are separated electrons and ions. The separated electrons are accelerated again by the electric field.
The sufficiently accelerated electrons come into collision with other gas atoms. In this case, another ionization may occur.
The ions are accelerated in opposition direction to the electrons. When the ions come into collision with a protection layer of MgO at a cathode, secondary electrons are discharged. The secondary electrons are accelerated by the electric field and come into collision with other gas atoms. In this case, the number of the electrically separated electrons gradually increases. If the number of the secondary electrons generated by collision of ions with the protection layer increases, the number of the gas atoms to be ionized increases. As a result, flow of the electrons or ions rapidly increases. This is called discharge.
At this time, it takes about several hundreds of ns or several Us to reach discharge after applying the electric field. This is called a discharge lag. The discharge lag includes a statistic time lag and a formative time lag. The formative time lag is caused by some factors such as kinds and pressure of gas, a structure of a cell, and discharge coefficient of the secondary electrons of the protection layer. The discharge lag is concerned in a width of a pulse for driving of the plasma display panel.
The formative time lag is generally within the range of several hundreds of ns while the statistic time lag is within the range of several hundreds of ns to several μs. If the priming particles exist at a sufficient concentration, the statistic time lag is set within several hundreds of ns. However, if the priming particles do not exist at a sufficient concentration, delay may occur for 3 μs to 4 μs. The most priming particles exist directly after discharge. The number of the priming particles is reduced as they are diffused to the discharge space, recombined, excited, and transited to the ground state.
The concentration of the priming particles from the time when discharge occurs to 30 μs does not affect the statistic time lag of the next discharge. However, the concentration of the priming particles after 30 μs has elapsed affects the statistic time lag of the next discharge.
For address discharge, if pulses are applied to the scan electrodes and the address electrodes, the discharge is completed within a desired time (generally, 3 μs) where the priming particles exist sufficiently. Thus, wall charges occur sufficiently. However, in the related art plasma display panel, it is likely that the priming particles do not exist sufficiently and thus the discharge is not completed within a desired time. In this case, address discharge may not occur in the discharge cell. This is called addressing failure or mis writing.
As described above, the related art plasma display panel has several problems.
Discharge lag is not constant due to deficiency of the priming particles for use in the priming effect. This could lead to address failure. Accordingly, to sufficiently generate wall charges, it is necessary to widen the width of the scan pulse applied to the scan electrodes at a constant level or greater. In this case, a problem arises in that a sustain time period is reduced if resolution becomes higher.